B2.2 Challenges Of Size Flashcards
Adaptations of multicellular organisms
High SA:V ratio on exchange surfaces as diffusion is difficult as size increases
How nutrients are spread
Animals - circulatory system
Plants - xylem and phloem tubes
Arteries
Thick and elastic outer layers to withstand pressure and recoil blood to push forward
Veins
Thin outer layers due to low pressure and presence of valves to prevent backflow
Capillaries
1 cell thick for better diffusion and links arteries and veins to body tissue
Heart
Read cardiovascular system in Extra Decks
Blood
Red- carries oxygen
White - large cell with nucleus to create antibodies against disease
Platelets- blood clotting
Plasma - 90% water and where all nutrients except oxygen are carried in
Plant circulatory system
Xylem - transports water and nutrients from roots to rest of plant
Phloem - transport products of photosynthesis (glucose) to rest of plant
Vascular bundles (xylem + phloem) is for supporting the leaves, the stem and roots
Xylem
Carries water and nutrients One way No end walls Thick walls of lignin to provide support Made of dead cells
Phloem
Carries sugars
2 way flow
Has end walls that allow sugars to pass through
Made of living cells
Transpiration
Loss of water from plants leaves
Transpiration stream
Water is lost from leaves
Low pressure water in leaves, high pressure at the roots
High pressure water from roots move to low pressure leaves through the xylem
How is water loss (transpiration) controlled?
Cuticle (thin waxy layer on leaf) prevents uncontrolled water loss
Guard cells open up stomata when full of water (turgid)
Guard cells close stomata when lack of water (plasmolysed)
Plant wilt
When water loss>water intake
Stomata will close to stop further water loss and photosynthesis will cease
How is rate of photosynthesis measured
On a potometer
Place air bubble in capillary tube
As water moves up plant, the air bubble moves
The rate at which the air bubble moves(s=d÷t) is the rate of transpiration
